how to modify hexa mesh

Hi,

I am newbie for solid meshing.

I imported *.inp file which is hexahedral meshed by 3rd program.

After I imported it, it looks like, the model is composed of bunch of elements. (no solid, no surface, no nodes..)

and some of the elements are missing and not in the right shape.

How can I convert elements to solid.. so that I can modify solid mesh?

and how to modify????